In a typical sprinkler system, a single water source supplies water simultaneously to several sprinkler outlets, interconnected by a network of underground supply pipes. Generally, at each outlet, a vertical riser pipe extends upward from a T-fitting or elbow in the supply pipe to the surface, where it is capped by a sprinkler head.
When designing a sprinkler system to spread water over a specified area, the water pressure, water flow volume, and the number, placement and type of sprinkler heads must all be considered. If a sprinkler head becomes dislodged, the system will generally not function properly. First, the water flow through that particular outlet will increase dramatically due to the reduced resistance. Second, this increased flow will not be dispersed, often causing localized flooding or erosion. Third, the water flow to the remaining outlets will be diminished, causing incomplete watering by the remainder of the circuit.
Therefore, it would be beneficial to have a mechanism which would shut off the water flow through an outlet from which the sprinkler head has become dislodged. This would prevent the increased, undispersed flow through that particular outlet, as well as the decreased water flow through the remaining sprinklers.
Specific .mechanisms have been designed to automatically shut off the flow of water through a sprinkler outlet in the absence of a sprinkler head. Generally, the existing mechanisms rely upon hydraulic pressure-the local increase in water flow due to the missing sprinkler head-to close a valve, thereby shutting off water flow through the outlet.
For example, both U.S. Pat. No. 1,432,386 to Curney ("the '386 patent") and U.S. Pat. No. 5,174,500 to Yianilos ("the '500 patent") describe devices which employ valves held open by physical contact with the sprinkler head. In each of these devices, a valve seat is located downstream of a valve element. The downstream flow of the valve element is impeded by the presence of the sprinkler head. When the sprinkler head becomes dislodged, the valve element is forced by the flow downstream until it closes the valve. The water pressure behind the valve keeps the valve element closed.
U.S. Pat. No. 4,736,889 to Shephenson ("the '889 patent") and U.S. Pat. No. 4,842,198 to Chang ("the '198 patent") both describe devices in which the valve is held open by a spring which is calibrated to overcome the normal flow through the outlet when the sprinkler head is in place. In these devices, the valve is again shut by the increased local water flow at the outlet when a sprinkler head becomes dislodged. In these cases, the increased flow overcomes the resistance provided by the spring and closes the valve.
U.S. Pat. No. 4,825,897 to Shade ("the '897 patent") describes a device, for use in vertical riser pipes, employing a weighted spherical valve member which is calibrated to float in the housing of the valve during normal flow conditions. When the sprinkler head becomes dislodged, the increased flow forces the sphere up, against the force of gravity, so that the sphere closes the valve.
One major disadvantage of the above-described systems is that each of these devices rely upon hydraulic forces to close the valve. Nothing holds the valve closed when the water pressure behind the valve is discontinued. This is especially problematic when it is desirable to provide the system with a mechanism to signal that a sprinkler head has been dislodged.
The mechanism described in the '500 patent and the '889 patent each allow for a continued, but greatly reduced, stream of water through the outlet when the sprinkler head is dislodged, and this stream can act to signal the absence of the sprinkler head. This stream will, however, cease when the water flow is terminated. Therefore, these devices do not provide an adequate signal when the water is not flowing.
Accordingly, there is a need for an improved sprinkler valve which will automatically seal a sprinkler outlet should the sprinkler head become dislodged, and will retain its seal regardless of whether the water is flowing in the system. There is an additional need for such an improved valve to include a means for signaling the absence of a sprinkler head at the outlet even in the absence of water flow. It would be particularly helpful if the indicator would work regardless of whether water was flowing through the system, so that it could be inspected and repaired without having the water flowing. This problem is not an obvious one, and none of the cited patents even recognizes it.